On Sun, Apr 21, 2019 at 01:07:08PM -0700, [email protected] wrote: > On April 21, 2019 11:28:42 AM PDT, Ingo Molnar <[email protected]> wrote: > > > >* Alexey Dobriyan <[email protected]> wrote: > > > >> TASK_SIZE macro is quite deceptive: it looks like a constant but in > >fact > >> compiles to 50+ bytes. > >> > >> Space savings on x86_64 defconfig: > >> > >> add/remove: 1/0 grow/shrink: 3/24 up/down: 77/-2247 (-2170) > >> Function old new delta > >> _task_size - 52 +52 > >> mpol_shared_policy_init 344 363 +19 > >> shmem_get_unmapped_area 92 97 +5 > >> __rseq_handle_notify_resume.cold 34 35 +1 > >> copy_from_user_nmi 123 113 -10 > >> mmap_address_hint_valid 92 56 -36 > >> arch_get_unmapped_area_topdown 471 435 -36 > >> tlb_gather_mmu 164 126 -38 > >> hugetlb_get_unmapped_area 774 736 -38 > >> __create_xol_area 497 458 -39 > >> arch_tlb_gather_mmu 160 120 -40 > >> setup_new_exec 380 336 -44 > >> __x64_sys_mlockall 378 333 -45 > >> __ia32_sys_mlockall 378 333 -45 > >> tlb_flush_mmu 235 189 -46 > >> unmap_page_range 2098 2048 -50 > >> copy_mount_options 518 465 -53 > >> __get_user_pages 1737 1675 -62 > >> get_unmapped_area 270 204 -66 > >> perf_prepare_sample 1176 1098 -78 > >> perf_callchain_user 549 469 -80 > >> mremap_to.isra 545 457 -88 > >> arch_tlb_finish_mmu 394 305 -89 > >> __do_munmap 1039 927 -112 > >> elf_map 527 409 -118 > >> prctl_set_mm 1509 1335 -174 > >> __rseq_handle_notify_resume 1116 906 -210 > >> load_elf_binary 11761 11111 -650 > >> Total: Before=14121337, After=14119167, chg -0.02% > >> > >> Signed-off-by: Alexey Dobriyan <[email protected]> > >> --- > >> > >> arch/x86/include/asm/processor.h | 4 ++-- > >> arch/x86/kernel/Makefile | 1 + > >> arch/x86/kernel/task_size_64.c | 9 +++++++++ > >> 3 files changed, 12 insertions(+), 2 deletions(-) > >> > >> --- a/arch/x86/include/asm/processor.h > >> +++ b/arch/x86/include/asm/processor.h > >> @@ -887,8 +887,8 @@ static inline void spin_lock_prefetch(const void > >*x) > >> > >> #define TASK_SIZE_LOW (test_thread_flag(TIF_ADDR32) ? \ > >> IA32_PAGE_OFFSET : DEFAULT_MAP_WINDOW) > >> -#define TASK_SIZE (test_thread_flag(TIF_ADDR32) ? \ > >> - IA32_PAGE_OFFSET : TASK_SIZE_MAX) > >> +unsigned long _task_size(void); > >> +#define TASK_SIZE _task_size() > >> #define TASK_SIZE_OF(child) ((test_tsk_thread_flag(child, > >TIF_ADDR32)) ? \ > >> IA32_PAGE_OFFSET : TASK_SIZE_MAX) > >> > >> --- a/arch/x86/kernel/Makefile > >> +++ b/arch/x86/kernel/Makefile > >> @@ -46,6 +46,7 @@ CFLAGS_irq.o := -I$(src)/../include/asm/trace > >> > >> obj-y := process_$(BITS).o signal.o > >> obj-$(CONFIG_COMPAT) += signal_compat.o > >> +obj-$(CONFIG_X86_64) += task_size_64.o > >> obj-y += traps.o idt.o irq.o irq_$(BITS).o > >> dumpstack_$(BITS).o > >> obj-y += time.o ioport.o dumpstack.o nmi.o > >> obj-$(CONFIG_MODIFY_LDT_SYSCALL) += ldt.o > >> new file mode 100644 > >> --- /dev/null > >> +++ b/arch/x86/kernel/task_size_64.c > >> @@ -0,0 +1,9 @@ > >> +#include <linux/export.h> > >> +#include <linux/sched.h> > >> +#include <linux/thread_info.h> > >> + > >> +unsigned long _task_size(void) > >> +{ > >> + return test_thread_flag(TIF_ADDR32) ? IA32_PAGE_OFFSET : > >TASK_SIZE_MAX; > >> +} > >> +EXPORT_SYMBOL(_task_size); > > > >Good idea - but instead of adding yet another compilation unit, why not > > > >stick _task_size() into arch/x86/kernel/process_64.c, which is the > >canonical place for process management related arch functions? > > > >Thanks, > > > > Ingo > > Better yet... since TIF_ADDR32 isn't something that changes randomly, perhaps > this should be a separate variable?
Maybe. I only thought about putting every 32-bit related flag under CONFIG_COMPAT to further eradicate bloat (and force everyone else to keep an eye on it, ha-ha).
